CHAPTER 56 THE EUSTACHIAN TUBE The primary function of the Eustachian tube is the maintenance of equal air pressure on each side of the tympanic membrane, normally the atmo- spheric pressure. Air reaches the middle ear by way of the Eustachian tube which is closed in its cartilaginous part but is opened by the movements of swallowing or yawning. The passage of air or fluid along the tube occurs more freely from middle ear to nasopharynx than in the reverse direction except in infants whose tube is wider and has a more horizontal course. Obstruction of the Eustachian tube can result from causes within its lumen or from causes arising at either end in the nasopharynx or the middle ear. When blockage of the tube occurs air within the middle ear is absorbed, the relative decrease in pressure being accompanied by inward retraction of the drumhead and congestion of the tympanic mucosa. Increase in the middle ear vacuum results in the formation of a transudate from the vessels and in some cases small haemorrhages may occur in the middle ear. ACUTE SALPJNGITIS Inflammatory reaction in the Eustachian tube is a frequent accompaniment of the common cold or of a severe bout of hay fever. In the majority of these cases the middle ear is not involved, in others with a more severe infec- tion otitis media may develop. The condition is associated with slight deaf- ness and a feeling of 'stuffiness' in the ear which may be temporarily relieved by swallowing. 'Popping' or 'crackling' noises may be complained of or there may be a more continuous tinnitus. Pain may radiate to the ear on nose-blowing but a more severe or persistent pain suggests the onset of otitis media. Examination of the nose and nasopharynx will frequently reveal evidence of an acute upper respiratory infection or of an allergic state. In a few cases the pharyngeal opening of the tube may be seen to be inflamed and prominent. On otoscopy the drumhead shows retraction with alteration or absence of the cone of light (see Plate X, 2). Vascular injection may be seen in the superficial vessels of the drumhead but quite often the drumhead is normal. TREATMENT. Decongestant nasal drops such as 1 per cent ephedrine hydro- chloride in normal saline should be instilled with the patient recumbent and the head extended and rotated to the affected side. No attempt should be made to inflate the Eustachian tube, and blowing of the nose should be reduced to the minimum, sniffing being preferable. Treatment should also be directed to the nasal and nasopharyngeal conditions.